1. Field of the Invention
The present invention relates to a method of fabricating nano-scale or molecular scale devices using fluidic assembly and novel devices produced thereby. More particularly, the present invention relates to a novel production method for electrical and dielectrical devices. Also, the invention relates to the production of fluidic structures which may be on the nano-scale, as desired. The invention further relates to the use of such structures in nano-particle and molecular scale applications such as sorters, filters, molecular electronics, sensors, and “molecular readers”.
2. Description of the Prior Art
Molecular scale electrical and dielectric devices normally consist of molecules contacted by a metal electrode and an electrolyte or by two metal electrodes. Generally the molecules are positioned using a self-assembling monolayer or monolayers (SAM) approach. These molecular-scale devices have attracted a great deal of interest because of their potentially wide impact on numerous technologies in applications such as micro diodes, micro switches, micro wires, and micro electric/dielectric and electrochemical sensors.
In such devices, the characteristics of the molecules selected are very important because the intent is to have the molecules determine the function of the device. For example, the molecule 4-thioacetylbiphenyl can form a SAM that can be used as a molecular wire by transporting electrons through the layer under certain conditions. In another example of a molecular device made using SAMs, a molecular switch has been demonstrated in which the bipyridinium molecule switches its conductivity on and off by changing its oxidation state. Devices using positioned, contacted molecules have additional potential in biotechnological applications. For example, it has been shown that SAM devices can detect certain target DNA, RNA, and proteins by hybridization, and can identify certain diseases and infections through determining specific DNA sequences. There have been a number of fabrication approaches for these devices, but most of the techniques are complex and non-manufacturable.
The growing demand for structures and detectors on the nano-particle and molecular scale has prompted considerable research by the nanofabrication community into the development of nanoscale gaps and pores. These nanoscale structures and devices are being proposed for use in applications such as molecular electronics, nucleic acid sequencing, the driving of unique chemical reactions, molecular filtration, chemical and electro-chemical sensing, and single molecule detection. A popular method of nanopore formation, which is being explored, is ion beam bombardment of micron, sub-micron, or nano-scale holes into molecular-scale pores (Li J, et al. Nature, 412 (6843):166–169 Jul. 12, 2001). In this approach, the starting holes are usually fabricated using standard photolithography. However, the problems associated with ion bombardment fabrication and dimensional control can be challenging to overcome. This is an immense problem when attempting to use this approach to produce high yield, low cost, manufacturable nano-scale structures for these applications on inexpensive substrates such as glasses, plastics or metal foils. In addition, approaches such as this create a pore, which in itself, does not perform the electrical or electrochemical biasing or monitoring. This functioning must be added. Other groups have produced channel structures for sorting and detection [J. Han and H. G. Craighead, Science 288: 1026(2000).] but these (1) lack the unique process flow and materials approach of this invention, attributes which lead to a manufacturable product, (2) lack attaining the nano-scale feature sizes disclosed here, (3) lack the precise gap (pore) spacing available with our approach, or (4) lack all these features.
In the present invention, the gap or pore can be defined by a material or materials which will allow self-assembly, allow chemical assembly, surface chemistry directed assembly, allow electric field guided assembly, allow steric assembly, or allow all of these. This allows controlled positioning of molecules or nano-particles in applications. It also allows valving materials to be positioned in the gap and to be controlled by gap electric fields, thermal changes, pH changes, and chemical changes when and if desired. The gap (pore) spacing can be directly fabricated with our approach to be a small as 1 nm. With our unique use of self-assembly, electro-less deposition, electrochemical plating, etching or electrochemical etching the gap spacing can be controllably further reduced or increased, as required.
One of the most challenging aspects of micro and nanofluidic design, fabrication and use is the control of fluid movement in complex devices. In this invention, the inventors describe a novel method for nano and microfluidic valve fabrication using polar, inducibly polar or liquid crystal molecules constrained within nano or microscale devices.
Accordingly, it is an object of the present invention to provide a new and improved method of producing fluidic, electrical or dielectrical devices on the molecular-scale or nano-scale.
Another object of the present invention is to provide molecular-scale or nano-scale devices which make use of fluidic assembly during fabrication or use.